How we use Go to build APIs PubNative best practices and patterns. Kostiantyn Stepaniuk PubNative GmbH

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Britton Johnston
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1 How we use Go to build APIs PubNative best practices and patterns Kostiantyn Stepaniuk PubNative GmbH

2 1/17 About PubNative Adtech company which connects publishers and advertisers through its technology First line of the API code was written in December 2013 in Ruby In November 2014 we migrated to Go API and supportive utilities have 200K lines of Go code We process 12M req/min Response time below 100ms We are connected to 197 partners with who we are doing real-time auction At a peak, we send 12M*197=2.364B outbound req/min

3 2/17 What challenges we have Competitive: cost-e cient and high-performing Resilient: survives the outage of any used service, DB, queue, cache, etc. Quick TTM: 1-2 products/year Productivity: 3043 PRs closed since 2013 or 2 PRs/day E ciency: product/tech task split 85/15, developing by 4 people (of 14 engineers)

4 3/17 How we do it Make it simple Make it boring Focus on what matters

5 4/17 Learn techniques Painted in 1897 by 15-year-old boy

6 5/17 And then improve Painted in 1955 by our 74-year-old boy :)

7 6/17 Use the same structure

8 7/17 Full control over HTTP protocol http.handlefunc("/handle/b", func(http.responsewriter, *http.request) {) http.handlefunc("/handle/a", func(http.responsewriter, *http.request) {) http.handlefunc("/basic_auth", func(w http.responsewriter, r *http.request) { usr, pwd, _ := r.basicauth() if usr!= "user" pwd!= "password" { w.header().set("www-authenticate", `Basic realm="application"`) w.writeheader(401) ) No powerful URL routers like gorilla/mux ( because of performance penalty and decreasing clarity. Go provides all the necessary wrappers Don't carry parameters in the path, use a query string or a request payload We need to know what happens under the hood to optimize

9 8/17 Use explicit types, avoid interfaces type App struct { Redis *redis.client // explicit name HB *honeybadger.client //commonly used abbreviation We solve speci c problems with concrete tools Clear understanding what is used and how Renaming can be done in one command in your favorite editor type ObjectA struct{ // Do we really need to have one interface? type ObjectB struct{ // Or we can keep them separately func (o ObjectA) Run(task int) bool { func (o ObjectB) Do(task int) bool { Got a challenge, try to solve it in the best way possible and then think of generalizing, not another way around

10 9/17 One way of doing things type A struct { B B type B struct { C C type C struct { D string a := A{ a.b.c.d // access D through chain a.getd() // NO helper methods a.c.d // NO aliases It also applies how to create pools, integrates 3rd parties or writes tests, etc.

11 10/17 Own pool of workers instead of what libraries provide func main() { pool := 10 ch := make(chan string, pool+10) // how many messages keep in a memory before taking an action for i := 0; i < pool; i++ { conn, err := redis.dial("tcp", ":6379") // connection per worker _ = err // handle error go func() { conn.do("hset", "hash", <-ch, 1) () Know how many connections are used No hidden bottlenecks, e.g., locks are used to manage the pool Easy to pro le the pool

12 11/17 Reserve a worker for a task func main() { jobs := make(chan chan int) // first chan to reserve a worker, second one to send a task for i := 0; i < 2; i++ { go worker(jobs) for i := 0; i < 10; i++ { job := make(chan int) select { case jobs <- job: fmt.println("reserve worker for task:", i) job <- i // build and send the task default: fmt.println("drop task:", i) func worker(jobs chan chan int) { for job := range jobs { task := <- job fmt.println("done task:", task)

13 12/17 Prefer non-blocking sending select { case ch1 <- "value1": // strategy 1 case ch2 <- "value2": // strategy 2 default: // take an action No time.after to control the pool Use bu ered channels for backpressure

14 13/17 Requirements for the pool Worker must know how to restart itself Fixed size of the pool and adjust per instance type Send metrics to centralized location and keep the current state on the instance What to pro le: How long does it take to process the task How many workers are busy right now What was the maximum number of concurrently occupied workers during lifetime of the process

$14/17 Single bu er type A struct { B int; _ int func main() { profile(func(){ for i := 0; i < 10; i++ { list := make([]*a, 1000) for i := 0; i < 1000; i++ { list[i] = &A{B: i ) func profile(fn$

15 14/17 Single bu er type A struct { B int; _ int func main() { profile(func(){ for i := 0; i < 10; i++ { list := make([]*a, 1000) for i := 0; i < 1000; i++ { list[i] = &A{B: i ) func profile(fn func()){ o := new(runtime.memstats) runtime.readmemstats(o) fn() n := new(runtime.memstats) runtime.readmemstats(n) fmt.printf("objects %v alloc %v", n.heapobjects-o.heapobjects, n.heapalloc - o.heapalloc)

16 15/17 Double bu ers func main() { profile(func(){ lists := make([][]*a, 2) lists[0] = make([]*a, 1000) lists[1] = make([]*a, 1000) for x := 0; x < 5; x++ { for y := 0; y < 1000; y++ { a := lists[0][y] if a == nil { a = &A{ a.b = x*y lists[0][y] = a ) lists[0], lists[1] = lists[1], lists[0]

17 16/17 Sometimes we have to write our library pubnative/mysqldriver-go ( GC optimized MySQL driver pubnative/mysqlproto-go ( Heap friendly implementation of the MySQL protocol

18 17/17 Keep the test code in one function func TestMyFunc(t *testing.t) { // 1. setup test // 2. define and execute test cases // 3. cleanup Keep tests straightforward, reading from top to bottom you should be able to understand how the code performs and what are requirements for it No helpers and abstractions in the test code De ne what's required to execute the code you test, nothing more

19 Thank you Kostiantyn Stepaniuk PubNative GmbH

go get my/vulnerabilities Green threads are not eco friendly threads

go get my/vulnerabilities Green threads are not eco friendly threads 1 Who ( Web Mobile ) penetration tester Code reviewer Programmer Roberto Clapis @empijei 2 Go Google s language Born in 2007 (quite